Internal Anatomy (Plate 106, fig. 2)

The septa vii/viii, viii/ix, ix/x, x/xi, xi/xii and xii/xiii are muscular and thickened.

Alimentary Canal. A rounded pharynx, covered dorsally and laterally by tufted salivary glands, occupies the first four segments. There is a thin-walled proventriculus in v, joining the pharynx to a large, thick-walled muscular gizzard in vi. The oesophagus extends from vii to xv and lacks oesophageal glands. The intestine commences in xvi. It is wide and thin-walled and has a marked typhlosole.

Vascular System. The dorsal blood vessel is unpaired. There is a short, narrow, supra-intestinal blood vessel running through segments x–xiii and giving rise to four pairs of dilated hearts in those four segments. The hearts arise from the supra-intestinal vessel as very narrow vessels, but dilate close to their origin into very wide vessels.

Reproductive System. There are two pairs of testes and their funnels in × and xi, and a single pair of ovaries with their funnels in xiii. The testes and ovaries are similar in form, dorso-ventrally flattened racemose structures attached to the anterior septa of their segments. There is one pair of spermathecae in ix. Each consists of a roughly ovoidal sac with a long hose-like diverticulum arising from the anterior aspect of its duct and describing a semicircle around the lateral aspect of the spermathecal sac, terminating behind the spermathecal sac in a dorsally directed portion (Plate 106, fig. 3). A pair of very long tubular prostates extend from xvii to xxvii, arising from narrow ducts in xvii. The distal portion of each prostate is thrown into coils. An elongate sac containing the penial chaetae lies on the medial aspect of each prostate and extends from xvii to xxiv. An individual penial chaeta removed from the sac is 5 mm. long. It is thus much shorter than the sac in which it is contained. It has an elongate, slightly irregular, gently curved shaft, with a gently recurved tip terminating in a point. There are two pairs of botryoidal vesiculae seminales in xi and xii surrounding the lateral and part of the dorsal aspects of the oesophagus.

The arrangement of the nephridia is most unusual for this genus. In segments ii–xx, small, coiled, paired meganephridia open to the exterior beside chaeta c, but close to the ventral nerve cord are found small clusters of micronephridial tubules. Posterior to xx, the meganephridia are large and no micronephridia occur.

Remarks. This species is obviously closely related to other species of Rhododrilus [especially to R. besti Benham (1904) and R. similis Benham (1905a)] but the co-existence of micronephridia and meganephridia in the first twenty segments poses a taxonomic problem of some importance. An earthworm possessing all the characters of Rhododrilus, but being partly or wholly micronephridial, should, according to Michaelsen's definitions of the sub-families of the Megascolecidae,